chore: Added release branch support to CI workflows

[hbelmiro]

Description of your changes:

Added support for release-<major>.<minor> branches (e.g., release-1.11) across all CI workflows, following the Kubeflow Pipelines branching convention.

Changes

• Documentation: Added "Branching Strategy" section to CONTRIBUTING.md
• Workflows: Added release-* to branch triggers in all 9 workflow files
• Scripts: Changed detect.py default from origin/main to origin/HEAD for generic local usage

Branch Convention

Branch	Base Image Tag
main	:main
release-1.11	:v1.11.0

Checklist:

Pre-Submission Checklist

• All tests and CI checks pass
• Pre-commit hooks pass without errors
• You have signed off your commits
• The title for your pull request (PR) should follow our title convention.
  Learn more about the pull request title convention used in this repository.

Additional Checklist Items for New or Updated Components/Pipelines

• metadata.yaml includes fresh lastVerified timestamp
• All required files
  are present and complete
• OWNERS file lists appropriate maintainers
• README provides clear documentation with usage examples
• Component follows snake_case naming convention
• No security vulnerabilities in dependencies
• Containerfile included if using a custom base image

[google-oss-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Details

Needs approval from an approver in each of these files:

• .github/OWNERS
• docs/OWNERS

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[hbelmiro]

/hold for a root approval too.

cc @mprahl @HumairAK

[Copilot]

Pull request overview

This PR adds support for release branches (e.g., release-1.11) across the CI/CD infrastructure, aligning with Kubeflow Pipelines' branching conventions. The changes enable CI workflows to run on both the main branch and release branches, and update documentation to guide contributors on the branching strategy.

Changes:

• Added comprehensive branching strategy documentation to CONTRIBUTING.md with examples
• Updated all 9 GitHub workflow files to trigger on both main and release-* branches
• Changed detect.py script default reference from origin/main to origin/HEAD for generic local usage

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/CONTRIBUTING.md	Adds new "Branching Strategy" section documenting release branch naming, purpose, and base image tag conventions
.github/workflows/yaml-lint.yml	Adds release-* to pull_request branches and normalizes quoting to single quotes
.github/workflows/validate-metadata-schema.yml	Adds release-* branch trigger for pull_request events
.github/workflows/scripts-tests.yml	Adds release-* branch triggers for both push and pull_request events with single quote normalization
.github/workflows/readme-check.yml	Adds release-* branch trigger for pull_request events
.github/workflows/python-lint.yml	Adds release-* to pull_request branches and normalizes quoting to single quotes
.github/workflows/markdown-lint.yml	Adds release-* to pull_request branches and normalizes quoting to single quotes
.github/workflows/component-pipeline-tests.yml	Adds release-* branch triggers for both push and pull_request events (uses double quotes)
.github/workflows/build-packages.yml	Adds release-* branch triggers for both push and pull_request events with single quote normalization
.github/workflows/base-image-check.yml	Adds release-* branch triggers for both push and pull_request events with single quote normalization
.github/scripts/detect_changed_assets/detect.py	Changes default base-ref from origin/main to origin/HEAD for generic local usage
.github/scripts/detect_changed_assets/README.md	Updates documentation to reflect origin/HEAD as the default base reference
.github/actions/detect-changed-assets/README.md	Updates input documentation table to clarify dynamic default for base-ref in PR context

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[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

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[gmfrasca]

should we be using uv here?

[hbelmiro]

We should. Fixed.

[gmfrasca]

let's be explicit that z-stream releases could be possible (not always x.y.0)

Suggested change

	| Branch | Purpose | Base Image Tag |
	|---------------------------|--------------------------------------------|-----------------------|
	| `main` | Active development | `:main` |
	| `release-<major>.<minor>` | Release maintenance (e.g., `release-1.11`) | `:v<major>.<minor>.0` |
	| Branch | Purpose | Base Image Tag |
	|---------------------------|--------------------------------------------|---------------------------------|
	| `main` | Active development | `:main` |
	| `release-<major>.<minor>` | Release maintenance (e.g., `release-1.11`) | `:v<major>.<minor>.<z-stream>` |

Also, it may be outside the scope of this PR but if not perhaps adding a quick section about z-stream releases here, their contents, and what triggers them may be useful

[hbelmiro]

Done.

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated no new comments.

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[gmfrasca]

/lgtm